Display screen or a portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing our new design;

The broken lines in the FIGURE show portions of the display screen orportion thereof with a graphical user interface which form no part ofthe claimed design.

The dash-dot broken lines shown in the FIGURE represent boundaries ofthe claimed design.

The graphical images shown within the dash-dot boundary lines form nopart of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.